Liquid crystal compounds having bis(trifluoromethyl) phenyl rings, liquid crystal compositions and liquid crystal display devices

ABSTRACT

The compound (1) having 2,3-bis(trifluoromethyl)-1,4-phenylene is stable chemically and has excellent miscibility with other liquid crystal compounds, large and negative dielectric anisotropy and proper optical anisotropy. A liquid crystal composition comprising the compound has large specific resistance and a large voltage holding ratio, and that the composition is useful for a liquid crystal display element. The compound (1) is represented by formula (1):  
     RaA 1 —Z 1  m A 2 —Z 2  n —A 3 —Z 3 —A 4 —Rb  (1)  
     wherein Ra and Rb independently are alkyl having 1 to 20 carbons, any —CH 2 — in the alkyl may be replaced by —O—, —S—, —CH═CH—, or —C≡C—, and any hydrogen may be replaced by halogen; A 1 , A 2 , A 3 , and A 4  independently are 1,4-cyclohexylene, 1,4-cyclohexenyleene, 1,3-dioxane-2,5-diyl, 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyridazine-3,6-diyl, or 2,3-bis(trifluoromethyl)-1,4-phenylene, any hydrogen in these rings may be replaced by halogen, and at least one of A 1 , A 2 , A 3 , and A 4  is 2,3-bis(trifluoromethyl)-1,4-phenylene; Z 1 , Z 2  and Z 3  independently are a single bond, —(CH 2 ) 2 —, —(CF 2 ) 2 —, —COO—, —OCO—, —CH 2 O—, —OCH 2 —, —CF 2 O—, —OCF 2 —, —CH═CH—, —CF═CF—, —C≡C—, —(CH 2 ) 4 —, —(CH 2 ) 3 O—, or —Q(CH 2 ) 3 —; m and n independently are 0 or 1.

TECHNICAL FIELD

[0001] This invention relates to a liquid crystal compound, a liquidcrystal composition and a liquid crystal display element. Moreparticularly, it relates to a new liquid crystal compound having2,3-bis(trifluoromethyl)-1,4-phenylene, a liquid crystal compositioncomprising the compound, and a liquid crystal display element comprisingthe composition.

[0002] A technical term of a liquid crystal compound is used as ageneric term for the compound having a liquid crystal phase and for thecompound having no liquid crystal phase and being useful as a componentof a liquid crystal composition. A liquid crystal compound(s), a liquidcrystal composition(s) and a liquid crystal display element(s) maybeexpressed herein simply as a compound(s), a composition(s) and anelement(s), respectively. A compound(s) represented by formula (1) toformula (12) is expressed herein as a compound(s) (1) to a compounds)(12), respectively. In formulas (2) to (12), structural units such as B,D, E, and so forth surrounded by a hexagon express ring B, ring D, ringE, and so forth. Other hexagons are 1,4-cyclohexylene, 1,4-phenylene andpyrimidine-2,5-diyl.

[0003] A liquid crystal display element is classified into TN (twistnematic), TN-TFT (twisted nematic-thin film transistor), BTN (bistabletwisted nematic), STN (super twisted nematic), IPS (in-plane switching),GH (guest host), DS (dynamic scattering), VA (vertical alignment), OCB(optically compensated bend), ECB (electrically controlledbirefringence), PC (phase change), and so forth based on display asystem.

[0004] For reducing consumption of electrical power in the element,driving voltage of the element is preferably low. Thus, a liquid crystalcomposition having a low threshold voltage is required. The thresholdvoltage (Vth) is represented by the following formula. See M. F. Leslie,Mol. Cryst. Liq. Cryst., 1970, 12, 57.

Vth=90 (K/γ ₀Δε)^(1/2)

[0005] In the formula, K is an elastic constant of a composition, ε₀represents an dielectric constant in a vacuum and Δε is dielectricanisotropy. As is seen in the formula, there are two ways to decreasethe threshold voltage, that is, increasing the dielectric anisotropy anddecreasing the elastic constant. As it is not easy to control theelastic constant, the composition having large dielectric anisotropy isnormally used. Accordingly, compounds having large dielectric anisotropyhave been developed.

[0006] Another problem in the liquid crystal display element is a narrowviewing angle. IPS mode and VA mode were reported in 1995 and 1997,respectively, to improve it. See Symposium on Liquid Crystals, 2A07,1995; ASIA DISPLAY '95, 557, 1995; ASIA DISPLAY '95, 1995; SID97 DIGEST,1997, 845. In these modes, a composition having negative dielectricanisotropy and small optical anisotropy is used.

[0007] The first object of this invention is to provide a liquid crystalcompound being stable chemically and having excellent miscibility withother liquid crystal compounds, large and negative dielectric anisotropyand proper optical anisotropy. The second object is to provide a liquidcrystal composition comprising the compound and having large specificresistance and a large voltage holding ratio, and a liquid crystaldisplay element comprising the composition.

SUMMARY OF THE INVENTION

[0008] The present inventors found that the compound (1) having2,3-bis(trifluoromethyl)-1,4-phenylene is stable chemically and hasexcellent miscibility with other liquid crystal compounds, large andnegative dielectric anisotropy and proper optical anisotropy. They alsofound that a liquid crystal composition comprising the compound haslarge specific resistance and a large voltage holding ratio, and thatthe composition is useful for a liquid crystal display element. Anembodiment of this invention for attaining the objects is as follows.Preferable examples of terminal groups, rings and bonding groups in thecompound (1) are also described.

[0009] 1. A liquid crystal compound represented by formula (1):

RaA₁—Z₁_(m)A₂—Z₂_(n)—A₃—Z₃—A₄—Rb  (1)

[0010] wherein Ra and Rb independently are alkyl having 1 to 20 carbons,any —CH₂— in the alkyl may be replaced by —O—, —S—, —CH═CH—, or —C≡C—,and any hydrogen may be replaced by halogen.

[0011] An example is given for the meaning of “any —CH₂— in the alkylmay be replaced by —O—, —CH═CH—, and so forth”. A part of the groups,when any —CH₂— in C₄H₉— is replaced by —O— or —CH═CH—, is C₃H₇O—, CH₃—O—(CH₂)₂—, CH₃—O—CH₂—O—, H₂C═CH—(CH₂)₃—, CH₃—CH═CH—(CH₂)₂—, andCH₃—CH═CH—CH₂—O—. As seen above, the term of “any” means “at least oneselected indiscriminately”. In consideration of stability of a compound,CH₃—O—CH₂—O— in which oxygen and oxygen are not adjacent is preferableto CH₃—O—O—CH₂— in which oxygen and oxygen are adjacent.

[0012] Preferable Ra or Rb is alkyl, alkoxy, alkoxyalkyl, alkoxyalkoxy,alkylthio, alkylthioalkoxy, alkenyl, alkenyloxy, alkenyloxyalkyl,alkoxyalkenyl, alkynyl, and alkynyloxy. These groups in which at leastone hydrogen is replaced by halogen are also preferable. Preferablehalogen is fluorine and chlorine. In these groups, a straight chain ispreferable to a branched chain. Branched Ra or Rb is preferable when thecompound (1) is optically active. Especially preferable Ra or Rb isalkyl, alkoxy, alkenyl, and alkenyloxy.

[0013] Preferable configuration of —CH═CH— in the alkenyl depends on theposition of a double bond. Trans-configuration is preferable in thealkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl,3-pentenyl, 3-hexenyl. Cis-configuration is preferable in the alkenylsuch as 2-butenyl, 2-pentenyl, 2-hexenyl. Alkenyl having preferableconfiguration has a high clearing point or a wide temperature range of aliquid crystal phase. See Mol. Cryst. Liq. Cryst., 1985, 131, 109.

[0014] Concrete Ra or Ra is methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, nonyl, decyl, methoxy, ethoxy, propoxy, butoxy,pentyloxy, hexyloxy, heptyloxy, methoxymethyl, methoxyethyl,methoxypropyl, ethoxymethyl, ethoxyethyl, ethoxypropyl, propoxymentyl,vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl,1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 2-propenyloxy,2-butenyloxy, 2-pentenyloxy, 1-propynyl, and 1-pentynyl.

[0015] Concrete Ra or Rb is also 2-fluoroethyl, 3-fluoropropyl,2,2,2-trifluoroethyl, 2-fluorovinyl, 2,2-difluorovinyl,2-fluoro-2-cyanovinyl, 3-fluoro-1-propenyl, 3,3,3-trifluoro-1-propenyl,4-fluoro-1-propenyl, and 4,4-difluoro-3-butenyl. Especially preferableRa or Rb is ethyl, propyl and pentyl.

[0016] A₁, A₂, A₃, and A₄ independently are 1,4-cyclohexylene,1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyridazine-3,6-diyl, or2,3-bis(trifluoromethyl)-1,4-phenylene. Any hydrogen in these rings maybe replaced by halogen, and at least one of A₁, A₂, A₃, and A₄ is2,3-bis (trifluoromethyl)-1,4-phenylene as shown below.

[0017] Preferable A₁, A₂, A₃, or A₄ is 1,4-cyclohexylene,1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene,2,5-difluoro-1,4.-phenylene, 2,6-difluoro-1,4-phenylene,2,3,5-trifluoro-1,4-phenylene, 2,3,5,6-tetrafluoro-1,4-phenylene,pyridine-2,5-diyl, 3-fluoropyridine-2,5-diyl, pyrimidine-2,5-diyl,pyridazine-3,6-diyl, and 2,3-bis(trifluoromethyl)-1,4-phenylene. Transis preferable to cis in the configuration of 1,4-cyclohexylene and1,3-dioxane-2,5-diyl.

[0018] Z₁, Z₂and Z₃ independently are a single bond, —(CH₂)₂—, —(CF₂)₂—,—COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CH═CH—, —CF═CF—, —C ≡C—,—(CH₂)₄—, —(CH₂)₃O—, or —O(CH₂)₃—.

[0019] Preferable Z₁, Z₂ or Z₃ is a single bond, —(CH₂)₂—, —COO—, —OCC—,—CH₂O—, —CF₂O—, —OCF₂—, —CH═CH—, —CF═CF—, —C≡C—, —(CH₂)₄— and —(CH₂)₃O—.Trans is preferable to cis in the configuration of —CH═CH— and —CF═CF—.

[0020] m and n independently are 0 or 1. The compound wherein m and nare 0 has two rings. The compound wherein m is 1 and n is 0 or m is 0and n is 1 has three rings. The compound wherein m and n are 1 has fourrings. The compound (1) may comprise an isotope such as ²H (deuterium)and ¹³C in an amount more than its natural abundance, because there isno large difference in the physical properties of the compound.

[0021] 2. The compound according to item 1 wherein m and n are 0 informula (1) described in item 1.

[0022] 3. The compound according to item 1 wherein m is 0 and n is 1 informula (1) described in item 1.

[0023] 4. The compound according to item 1 wherein m is 1 and n is 1 informula (1) described in item 1.

[0024] 5. The compound according to any one of items 1 to 4 wherein Raand Rb independently are alkyl having 1 to 20 carbons, alkoxy having 1to 19 carbons or alkenyl having 2 to 21 carbons.

[0025] 6. The compound according to any one of items 1 to 4 wherein Raand Rb independently are alkyl having 1 to 20 carbons, alkoxy having 1to 19 carbons or alkenyl having 2 to 21 carbons; and Z₁, Z₂ and Z₃independently are a single bond, —(CH₂)₂—, —(CH₂)₄—, —CF₂O—, or —OCF₂—.

[0026] 7. The compound according to item 6 wherein at least one of Z₁,Z₂ and Z₃ is —CF₂O—.

[0027] 8. A compound represented by formulas (a) to (m):

[0028] wherein Ra and Rb independently are alkyl having 1 to 20 carbons,any —CH₂— in the alkyl may be replaced by —O— or —CH═CH—, and anyhydrogen may be replaced by halogen; A₁, A₂, A₃, and A₄ independentlyare 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl,1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene,2,5-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene,2,3,5-trifluoro-1,4-phenylene, 2,3,5,6-tetrafluoro-1,4-phenylene,pyridine-2,5-diyl, 3-fluoropyridine-2,5-diyl, pyrimidine-2,5-diyl,pyridazine-3,6-diyl, or 2,3-bis(trifluoromethyl)-1,4-phenylene, and atleast one of A₁, A₂, A₃, and A₄ is2,3-bis(trifluoromethyl)-1,4-phenylene; Z₁, Z₂ and Z₃ independently area single bond, —(CH₂)₂—, —(CF₂)₂—, —COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—,—OCF₂—, —CH═CH—, —CF═CF—, —C≡C—, —(CH₂)₄—, —(CH₂)₃O—, or —O(CH₂)₃—; andm and n independently are 0 or 1.

[0029] 9. A liquid crystal composition comprising at least one compounddescribed in any one of items 1 to 8.

[0030] 10. The composition according to item 9, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (2), (3) and (4):

[0031] wherein R¹ is alkyl having 1-10 carbons, any —CH₂— in the alkylmay be replaced by —C— or —CH═CH—, and any hydrogen may be replaced byfluorine; X¹ is fluorine, chlorine, —OCF₃—OCHF₂, —CF₃, —CHF₂, —CH₂F,—OCF₂CHF₂, or —OCF₂CHFCF₃; rings B and D independently are1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or 1,4-phenylene in which anyhydrogen may be replaced by fluorine;

[0032] ring E is 1,4-cyclohexylene or 1,4-phenylene in which anyhydrogen may be replaced by fluorine; and Z⁴ and Z⁵ independently are—(CH₂)₂—, —(CH₂)₄—, —COO—, —CF₂O—, —OCF₂—, —CH═CH—, or a single bond;and L¹ and L² independently are hydrogen or fluorine.

[0033] 11. The composition according to item 9, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (5) and (6):

[0034] wherein R² and R³ independently are alkyl having 1 to 10 carbons,any —CH₂— in the alkyl may be replaced by —O— or —CH═CH— and anyhydrogen may be replaced by fluorine; X² is —CN or —C≡C—CN; ring G is1,4-cyclohexylene, 1,4-phenylene, 1,3-dioxane-2,5-diyl, orpyrimidine-2,5-diyl; ring J is 1,4-cyclohexylene, pyrimidine-2,5-diyl or1,4-phenylene in which any hydrogen may be replaced by fluorine; ring Kis 1,4-cyclohexylene or 1,4-phenylene; Z⁶ is —(CH₂)₂—, —COO—, —CF₂O—,—OCF₂—, or a single bond; L³, L⁴ and L⁵ independently are hydrogen orfluorine; and b, c and d independently are 0 or 1.

[0035] 12. The composition according to item 9, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (7), (8) and (9):

[0036] wherein R⁴ and R⁵ independently are alkyl having 1 to 10 carbons,any —CH₂— in the alkyl may be replaced by —O— or —CH═CH—, and anyhydrogen may be replaced by fluorine; rings M and P independently are1,4-cyclohexylene or 1,4-phenylene; Z⁷ and Z⁸ independently are—(CH₂)₂—, —COO— or a single bond; L⁶ and L⁷ independently are hydrogenor fluorine, and at least one of L⁶ and L⁷ is fluorine.

[0037] 13. The composition according to item 10, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (10), (11) and (12):

[0038] wherein R⁶ and R⁷ independently are alkyl having 1 to 10 carbons,any —CH₂— in the alkyl may be replaced by —O— or —CH═CH—, and anyhydrogen may be replaced by fluorine; rings Q, T and U independently are1,4-cyclohexylene, pyrimidine-2,5-diyl or 1, 4-phenylene in which anyhydrogen may be replaced by fluorine; Z⁹ and Z₁₀ independently are—C≡C—, —COO—, —(CH₂)₂—, —CH═CH—, or a single bond.

[0039] 14. The composition according to item 11, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (10), (11) and (12) described in item 13.

[0040] 15. The composition according to item 12, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (10), (11) and (12) described in item 13.

[0041] 16. The composition according to item 13, further comprising atleast one compound selected from the group consisting of the compoundsrepresented by formulas (5) and (6) described in item 11.

[0042] 17. The composition according to items 9 to 16, furthercomprising at least one optically active compound.

[0043] 18. A liquid crystal display element comprising the compositiondescribed in any one of items 9 to 17.

[0044] In the compounds (2) to (12), preferable groups are as follows.Straight alkyl is preferable to branched alkyl. Trans is preferable tocis in the configuration of 1,4-cyclohexylene and 1,3-dioxane-2,5-diyl.Meaning of the phrase in “any —CH₂— in the alkyl may be replaced by —O—or —CH═CH—” is described in item 1 of the embodiment. Symbols such asR¹, ring B, and so forth were used in plural compounds and these R¹ (orring B and so forth) may be identical or may be different each other.These compounds may comprise an isotope such as ²H (deuterium) and ¹³Cin an amount more than its natural abundance, because there is no largedifference in the physical properties of the compound.

DETAILED DESCRIPION OF THE PREFERRED EMBODIMENT

[0045] Firstly, the compound (1) of this invention is further explained.The compound (1) is two rings-, three rings- and four rings-compoundshaving 2,3-bis (trifluoromethyl)-1,4-phenylene. The compound is stronglystable physically and chemically and is excellent in miscibility withother compounds. A composition comprising the compound is stable underthe conditions adopted when an element is normally used. Keeping thecomposition even at low temperature does not allow the compound toseparate out as a solid. The compound has a large, negative dielectricanisotropy and a proper value of optical anisotropy.

[0046] Physical properties such as optical anisotropy can be controlledby properly selecting a terminal group, a ring and a bonding group ofthe compound (1). An effect of a kind of terminal groups Ra and Rb,rings A₁ to A₄, and bonding groups Z₁ to Z₃, on the physical propertiesof compound (1) will be explained below. By adding the compound (1) to acomposition, the physical properties of the compound (1) influencesthose of the composition. As the compound (1) has large and negativedielectric nisotropy, it is useful as a component in a composition forIPS mode and VA mode. The compound can also be added to a compositionfor modes such as TN, STN, TN-TFT, and so forth.

[0047] When Ra or Rb in the compound (1) is straight, a temperaturerange of a liquid crystal phase is wide and viscosity is small. When Raor Rb is branched, miscibility with other liquid crystal compounds isexcellent. The compound in which Ra or Rb is an optically active groupis useful as a chiral dopant. The addition of the compound to acomposition prevents a reversed twisted domain that is formed in anelement. The compound that Ra or Rb is not optically active group isuseful as a component of a composition.

[0048] When ring A₁, A₂, A₃, or A₄ in the compound (1) is 1,4-phenylenein which any hydrogen is replaced by halogen, pyridine-2,5-diyl or1,3-dioxane-2,5-diyl, dielectric anisotropy is large. When the ring is1,4-phenylene in which any hydrogen may be replaced by halogen,pyridine-2,5-diyl, pyrimidine-2,5-diyl, or pyridazine-3,6-diyl, opticalanisotropy is large. When the ring is 1,4-cyclohexylene,1,4-cyclohexenylene or 1,3-dioxane-2,5-diyl, optical anisotropy issmall.

[0049] When at least two rings are 1,4-cyclohexylene, a clearing pointis high, optical anisotropy is small, and viscosity is small. When atleast one ring is 1,4-phenylene, optical anisotropy is relatively large,orientational order parameter is large. When at least two rings are1,4-phenylene, optical anisotropy is large, a temperature range of aliquid crystal phase is wide, and a clearing point is high.

[0050] When a bonding group, Z₁, Z₂ or Z₃ is a single bond, —(CH₂)₂—,—CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CH═CH—, —CF═CF—, or —(CH₂)₄—, viscosityis small. When the bonding group is a single bond, —(CH₂)₂—, —CF₂O—,—OCF₂—, —CH═CH—, or —(CH₂)₄— viscosity is smaller. When the bondinggroup is —CH═CH— or —CF═CF—, a temperature range of a liquid crystalphase is wide, and a ratio of elastic constants is large. When thebonding group is —C≡C—, optical anisotropy is large.

[0051] When the compound (1) has two rings or three rings, viscosity issmall, and when it has three rings or four rings, a clearing point ishigh. As described above, the compound having desired physicalproperties can be obtained by selecting properly a kind of a terminalgroup, a ring, a bonding group, and the number of the ring.

[0052] Preferable example of the compound (1) is the compounds (1a-1) to(1d-9). Meaning for symbols of Ra, Rb, Z₁, Z₂ and Z₃ in these compoundsis identical to that described in item 1 of the embodiment. In rings of1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl,1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, orpyridazine-3,6-diyl present in these compounds, any hydrogen may bereplaced by halogen such as fluorine. A black dot in 1,4-cyclohexyleneand 1,3-dioxane-2,5-diyl means that configuration of these rings istrans.

[0053] The compound (1) can be prepared by an appropriate combination ofmethods in organic synthetic chemistry. A method of introducingobjective terminal groups, rings and bonding groups to a startingmaterial is described in books such as Organic Syntheses, John Wiley &Sons, Inc., Organic Reactions, John Wiley & Sons, Inc., ComprehensiveOrganic Synthesis, Pergamon Press, Shin-Jikken Kakagu Koza (Maruzen).

[0054] One example of a method for preparing2,3-bis(trifluoromethyl)-1,4-phenylene ring is shown in the followingscheme. A compound having this ring is prepared based on this method.This compound is a starting material for the preparation of the compound(1). After explaining the scheme, one example of the method for theformation of bonding groups will be described.

[0055] This example is based on the method described in Org. Lett.,2000, 2(21), 3345. Aniline derivative (B) is prepared by the Diels-Alderreaction of 1,1,1,4,4,4-hexafluoro-2-butyne with furan derivative (A) athigh temperature. This compound is converted to iodide (C) by theSandmeyer reaction described in Org. Synth. Coll., Vol. 2, 1943, 355.The compound (D) having Rb group is obtained by the alkylation of thecompound (C) with alkyl halide, alkenyl halide or alkynyl halide.Meaning for symbol of Rb in the compound (D) is identical to thatdescribed in item 1 of the embodiment. After the compound (D) isconverted to the boric acid derivative, the compound (G) is obtained byoxidation according to the method described in J. Am. Chem. Soc., 1960,82, 4708. The compound (G) is also prepared by alkylation of anilinederivative (B), followed by conversion to diazonium salt and then byhydrolysis.

[0056] The benzoic acid (E) is obtained by the reaction of the compound(D) with alkyllithium and then with carbon dioxide. The compound (E) isconverted to benzylbromide (F) by the reduction with lithium aluminumhydride and so forth and by halogenation with hydrobromic acid and soforth. On the other hand, benzaldehyde (H) is obtained from compound (E)by esterification followed by reduction with diisobutylaluminum hydrideand so forth.

[0057] Phenol (J) is prepared by the similar reaction using the furanderivative (I; R is alkyl) as a starting material instead of thecompound (A). The compound (G) having alkyl, alkenyl or alkynyl isobtained by the cross-coupling catalyzed by organometallic compounds ortransition metals, after converting a hydroxyl group in the compound (J)into a reactive functional group such as tosyloxy and mesyloxy. Thecross-coupling is described in Metal-Catalyzed Cross-Coupling Reactions(Wiley-VCH, 1998). The obtained phenol (G) is converted to the compound(K) by halogenation.

[0058] One example of the method for the formation of a bonding group,Z₁, Z₂ or Z₃, is first shown in a scheme, which is then explained initem (I) to item (XI). In the scheme, MSG¹ or MSG² is a monovalentorganic group having at least one ring. Plural MSG¹ (or MSG²) may beidentical or different each other. The compounds (1A) to (1K) correspondto the compound (1).

[0059] (I) Formation of a Single Bond

[0060] The compound (1A) is prepared by the reaction of arylboronic acid(21) with the compound (22) in the presence of catalysts such as anaqueous solution of carbonate and tetrakis(triphenylphosphine)palladium.The compound (1A) is also prepared by the reaction of the compound (23)prepared by a known method with n-butyllithium and then zinc chloride,and with the compound (22) in the presence of a catalyst such asdichlorobis(triphenylphosphine)palladium.

[0061] (II) Formation of —COO— and —OCO—

[0062] The compound (24) is obtained by the reaction of the compound(23) with n-butyllithium followed by carbon dioxide. The compound (1B)is prepared by dehydration of the compound (24) and phenol (25) preparedby a known method in the presence of DDC (1,3-dicyclohexylcarbodiimide)and DMAP (4-dimethylaminopyridine). The compound having —OCO— is alsoprepared by this method.

[0063] (III) Formation of —CF₂O— and —OCF₂—The compound (26) is obtainedby treating the compound (1B) with a sulfurating agent such asLawesson's reagent. The compound (1C) having —CF₂O— is prepared byfluorination of the compound (26) with hydrogen fluoride-pyridinecomplex and NBS(N-bromosuccinimide). See M. Kuroboshi et al., Chem.Lett., 1992, 827. The compound (1C) is also prepared by fluorination ofthe compound (26) with (diethylamino) sulfur trifluoride. See W. H.Bunnelle et al., J. Org. Chem., 1990, 55, 768. The compound having—OCF₂— is also prepared by this method.

[0064] (IV) Formation of —CH═CH—

[0065] The compound (23) is treated with n-butyllithium and thenformamide such as N,N-dimethylformamide to give aldehyde (28). Thecompound (1D) is prepared by the reaction of the aldehyde (28) withphoshine ylide which is generated by the treatment of phosphinium salt(27) prepared by a known method with a base such as potassiumt-butoxide. As cis isomer may be formed depending on the reactionconditions, it is isomerized to trans isomer by a known method onrequest.

[0066] (V) Formation of —(CH₂)₂—

[0067] The compound (1E) is prepared by hydrogenation of the compound(1D) in the presence of a catalyst such as palladium carbon.

[0068] (VI) Formation of —(CH₂)₄—

[0069] The compound having —CH═CH—(CH₂)₂— is obtained using phosphoniumsalt (29) instead of the phosphonium salt (27) according to the methoddescribed in item (IV). The compound is subjected to a catalytichydrogenation to prepare the compound (1F).

[0070] (VII) Formation of —C≡C—

[0071] The compound (23) is reacted with 2-methyl-3-butyn-2-ol in thepresence of catalysts of palladium dichloride and copper halide,followed by deprotection under the basic conditions to give the compound(30). The compound (1G) is prepared by the reaction of the compound (30)with the compound (22) in the presence of catalysts of palladiumdichloride and copper halide.

[0072] (VIII) Formation of —CF═CF—

[0073] The compound (31) is obtained by the reaction of the compound(23) with n-butyllithiun and then tetrafluoroethylene. The compound(1H.) is prepared by the reaction of the compound (22) withn-butyllithiun and then the compound (31).

[0074] (IX) Formation of —CH₂O— and —OCH₂—

[0075] The compound (32) is obtained by reduction of the compound (28)with a reducing agent such as sodium borohydride. The compound (33) isobtained by halogenation of the compound (32) with hydrobromic acid. Thecompound (1J) is prepared by the reaction of the compound (33) with thecompound (25) in the presence of potassium carbonate.

[0076] (X) Formation of —(CH₂)₃O— and —O(CH₂)₃—

[0077] The compound (1K) is prepared using the compound (34) instead ofthe compound (32) according to the method of item (IX)—

[0078] (XI) Formation of —(CF₂)₂—

[0079] The compound having —(CF₂)₂— is obtained by fluorination ofdiketone (—COCO—) with sulfur tetrafluoride in the presence of acatalyst of hydrogen fluoride according to the method described in J.Am. Chem. Soc., 2001, 123, 5414.

[0080] Secondly, the composition of this invention is further explained.Amount of the compound (percentage) described below is weight percentbased on the total weight of the composition. The composition maycomprise plural compounds selected only from the compound (1).Preferably, the composition comprises at least one compound selectedfrom the compound (1) in the ratio of 1 to 99%. The composition mayfurther comprise at least one compound selected from the groupconsisting of the compounds (2), (3) and (4), at least one compoundselected from the group consisting of the compounds (5) and (6), or atleast one compound selected from the group consisting of the compounds(7), (8) and (9). The composition may further comprise at least onecompound selected from the group consisting of the compounds (10), (11)and (12) for the purpose of controlling a temperature range of a liquidcrystal phase, viscosity, optical anisotropy, dielectric anisotropy,threshold voltage, and so forth. The composition may further compriseother compounds for the purpose of controlling the physical properties.

[0081] The compounds (2), (3) and (4) are used mainly for thecomposition for TN-TFT mode, because dielectric anisotropy is positiveand large, and thermal and chemical stability is excellent. In thecomposition, the amount of these compounds is 1 to 99%. Preferableamount is 10 to 97%. More preferable amount is 40 to 95%. The compounds(10), (11) or (12) may be further added to the composition for thepurpose of controlling a temperature range of a liquid crystal phase,viscosity, optical anisotropy, dielectric anisotropy, or thresholdvoltage.

[0082] The compounds (5) and (6) are used mainly for the composition forSTN and TN modes, because dielectric anisotropy is positive and verylarge. These compounds are used for the purpose of widening atemperature range of a liquid crystal phase, controlling viscosity andoptical anisotropy, decreasing threshold voltage, improving sharpness ofthe threshold voltage, and so forth. In the composition for STN or TFTmode, the amount of compound (5) or (6) is 1 to 99%. Preferable amountis 10 to 97%. More preferable amount is 40 to 95%. The compounds (10),(11) or (12) maybe further added to the composition for the purpose ofcontrolling a temperature range of a liquid crystal phase, viscosity,optical anisotropy, dielectric anisotropy, or threshold voltage.

[0083] The compounds (7), (8) and (9) are used mainly for thecomposition for VA mode, because dielectric anisotropy is negative. Thecompound (7) is used for the purpose controlling viscosity, opticalanisotropy and threshold voltage. The compound (8) is used for thepurpose of increasing a clearing point, increasing optical anisotropyand decreasing threshold voltage, and so forth. With an increase in theamount of these compounds, threshold voltage is decreased and viscosityincreased. Thus, smaller amount is preferable as long as the requiredvalue of threshold voltage is satisfied. As dielectric anisotropy ofthese compounds is negative and its absolute value is 5 or less,preferable amount is 40% or more. More preferable amount is 40 to 80%.For the purpose of controlling an elastic constant and avoltage-transmittance curve, these compounds may be added to acomposition having positive dielectric anisotropy, preferably in theamount of 30% or less.

[0084] The absolute value of dielectric anisotropy is small in thecompounds (10), (11) and (12). The compound (10) is used mainly for thepurpose of controlling viscosity and optical anisotropy. The compounds(11) and (12) is used for the purpose of increasing a clearing point towiden a temperature range of a liquid crystal phase or controllingoptical anisotropy. With an increase in the amount of the compounds(10), (11) and (12), threshold voltage is increased and viscosity isdecreased. Thus, larger amount is preferable as long as the requiredvalue of threshold voltage is satisfied. in the composition for TN-TFTmode, preferable amount of these compounds is 40% or less. Morepreferable amount is 35% or less. In the composition for STN or TN mode,preferable amount is 70% or less. More preferable amount is 60% or less.

[0085] Preferable compounds (2) to (12) are compounds (2-1) to (2-9),compounds (3-1) to (3-97), compounds (4-1) to (4-33), compounds (5-1) to(5-56), compounds (6-1) to (6-3), compounds (7-1) to (7-3), compounds(8-1) to (8-5), compounds (9-1) to (9-3), compounds (10-1) to (10-11),compounds (11-1) to (11-18) and compounds (12-1) to (12-6),respectively. In these compounds, the symbols R¹, R², R³, R⁴, R⁵, R⁶,R⁷, X¹, and X² have the same meaning as described in item 1 of theembodiment of this invention.

[0086] The composition of this invention is prepared by known methods.For example, compounds as a component are mixed and dissolved each otherby heating. Physical properties of the composition may be controlled bythe addition of appropriate additives to the composition. Such additivesare well known by those skilled in the art. A chiral dopant is added forthe purpose of inducing a helical structure of liquid crystals to givedesired twist angle. Examples of the chiral dopant are optically activecompounds (Op-1) to (Op-12) given above.

[0087] The pitch of a twist is controlled by the addition of the chiraldopant to the composition. Preferable pitch is in the range from 40 to200 micrometers for TN and TFT modes. Preferable pitch is in the rangefrom 6 to 20 micrometers for STN mode. Preferable pitch is in the rangefrom 1.5 to 4 micrometers for BTN mode. Relatively larger amount of achiral dopant is added to the composition for PC mode. At least twochiral dopants may be added for the purpose of controlling temperaturedependence of the pitch.

[0088] The composition of this invention can be used for modes of TN,TN-TFT, STN, GH, DS, ECB, and so forth. The composition for GH mode isprepared by adding a dichroic dye which is a compound such asmerocyanine, styryl, azo, azomethine, azoxy, quinophthalone,anthraquinone, tetrazine, and so forth. The composition of thisinvention can also be used for NCAP which is prepared bymicrocapsulating nematic liquid crystals, and a polymer dispersed liquidcrystal display element (PDLCD) which is prepared by forming athree-dimensional polymer network in liquid crystals, for example, apolymer network liquid crystal display element (PNLCD) and so forth.

EXAMPLES

[0089] Thirdly, the invention is further explained by the examples. Thisinvention is not limited by these examples. In a phase transitiontemperature of the compounds, C, Sm, SmA, SmB, N, and I are crystals, asmectic phase, a smectic A phase, a smectic B phase, a nematic phase,and an isotropic phase, respectively, and a phase transition in aparenthesis means that it is monotropic. Unit of the temperature is ° C.Obtained compounds were identified based on the data from NMR spectra,mass-spectra, and so forth. In NMR spectra, s is singlet, d is doublet,t is triplet, q is quartet, and m is multiplet. THF stands fortetrahydrofuran, DME stands for ethylene glycol dimethyl ether, and NBSstands for N-bromosuccinimide. The following composition was used forthe measurement of dielectric anisotropy (Δε, 25° C.) in the compound(1). A sample was prepared by adding 15 wt % of the compound (1) to 85wt % of this composition. A method of measurement will be describedlater. A value of dielectric anisotropy was calculated by extrapolatinga value measured.

Example 1

[0090]

[0091] (1) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenol

[0092] 1,1,1,4,4,4-Hexafluoro-2-butyne (7.2 g, 44.4 mmol) was condensedinto a 300 ml tube for sealing which had been cooled with liquidnitrogen, and 2-methoxyfuran (3.5 g, 35.7 mmol) and dried benzene (50ml) were further added slowly. After the tube was sealed, it was heatedat 85° C. for 5 hours in an oil bath. After unreacted1,1,1,4,4,4-hexafluoro-2-butyne was removed from the reaction mixture,the residue was concentrated under reduced pressure to afford paleyellow crystals. Recrystallization of the crystals from pentane gave thetitle compound (5.9 g, 64%; pale yellow crystals).

[0093] (2) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenyl4-(4-propylcyclohexyl)cyclohexanecarboxylate

[0094] A mixture of 4-methoxy-2,3-bis (trifluoromethyl)phenol (1.0 g,3.8 mmol), 4-(4-propylcyclohexyl)cyclohexanecarboxylic acid (0.97 g, 3.8mmol), dicyclohexylcarbodiimide (0.83 g, 4.0 mmol),4-dimethylaminopyridine (47 mg, 0.39 mmol), and dry methylene chloride(40 ml) was stirred at room temperature for two hours. Water (1 ml) wasadded to the reaction mixture, which was stirred for one hour, then thesolvent was removed under reduced pressure. The residue was purified bycolumn chromatography (silica gel, an eluent is toluene) to give thetitle compound (1.13 g, 59%, colorless crystals). The value of R_(f) ofthis compound was 0.68 (toluene) and dielectric anisotropy was −9.5(extrapolated).

[0095] Cr (86. 7 SmA) 129.1 N 164.9 I.

[0096]¹H-NMR (500 MHz, CDCl₃): δ 0.89 (t, ³J=7.1 Hz, 3H), 0.96-1.17 (m,11H), 1.30-1.36 (m, 2H), 1.50-1.57 (m, 2H), 1.75 (q, ²J=12.0 Hz, 4H),1.87 (d, ²J=10.7 Hz, 2H), 2.17 (d, ²J=11.1 Hz, 2H), 2.38-2.54 (m, 1H),3.95 (s, 3H), 7.24 (d, ³J=11.0 Hz, 2H), 7.26 (d, ³J=11.0 Hz, 2H).

[0097]¹⁹F-NMR (470 MHz, CDCl₃): δ −56.0 (q, ⁵J^(FF)=16.5 Hz, 3F), −55.2(q, ⁵J_(FF)=16.5 Hz, 3F).

[0098] MS(70 eV, CI), m/z(%): 495(100, MH⁺4), 494(85, M⁺).

Example 2

[0099]

[0100] (1) Preparation of4′-(4-propylcyclohexyl)-4-hydroxy-2,3-bis(trifluoromethyl)-1,1′-biphenyl

[0101] 4-Iodo-2,3-bis(trifluoromethyl)phenol (200 mg, 0.56 mmol)prepared in accordance with the method of Gui-Dong Zhu et. al., (OrganicLett., 2000, 2(21), 3345), Pd₂(dba)₃ (26 mg, 0.028 mmol),tri(o-tolyl)phosphine (26 mg, 0.084 mmol),4-(4-propylcyclohexyl)phenylboronic acid (275 mg, 1.12 mmol), K₃PO₄ (237mg, 1.12 mmol), and dry DME (7 ml) were placed in a 30 ml tube forsealing in an atmosphere of dry nitrogen and was sealed. The sealed tubewas heated for 6 hours in an oil bath at 80° C. The reaction mixture wascooled to room temperature, poured into diethyl ether (50 ml) and thenthe organic layer was washed twice with water (30 ml). After the organiclayer was dried over anhydrous magnesium sulfate, the solvent wasremoved under reduced pressure. The obtained residue was purified bycolumn chromatography (silica gel, an eluent is ethyl acetate) to givethe title compound (123 mg, 51%).

[0102] (2) Preparation of4′-(4-propylcyclohexyl)-4-methoxy-2,3-bis(trifluoromethyl)-1,1′-biphenyl

[0103] To a mixture of4′-(4-propylcyclohexyl)-4-hydroxy-2,3-bis(trifluoromethyl)-1,1′-biphenyl(100 mg, 0.23 mmol), potassium carbonate (32 mg, 0.23 mmol) and methanol(10 ml), methyl iodide (65.3 mg, 0.46 mmol) in an atmosphere of drynitrogen was added dropwise over 1 hour and was heated under reflux for3 hours. The reaction mixture was cooled to room temperature, pouredinto toluene (20 ml), and then the organic layer was washed twice withwater (20 ml). After the organic layer was dried over anhydrousmagnesium sulfate, the solvent was removed under reduced pressure. Theresidue was purified by column chromatography (silica gel, an eluent istoluene) to give the title compound (88.9 mg, 87%, colorless crystals).

Example 3

[0104]

[0105] (1) Preparation of4-iodo-2,3-bis(trifluoromethyl)-1-methoxybenzene

[0106] To a mixture of 4-iodo-2,3-bis(trifluoromethyl)phenol (2.0 g,5.61 mmol), potassium carbonate (0.78 g, 5.61 mmol) and methanol (20ml), methyl iodide (1.73 g, 12.2 mmol) was added dropwise over one hour,and was heated under reflux for additional one hour. Methanol (15 ml)was distilled off from the reaction mixture, and the residue wasextracted with diethyl ether (30 ml). The solvent was removed underreduced pressure, and the residue was distilled to give the titlecompound (1.27 g, 61%).

[0107] (2) Preparation of4-[1-hydroxy-4-(4-propylcyclohexyl)cyclohexyl]-2,3-bis(trifluoromethyl)-1-methoxybenzene

[0108] In an atmosphere of dry nitrogen, to4-iodo-2,3-bis(trifluoromethyl)anisole (1.27 g, 3.43 mmol) in dry THF(30 ml), n-BuLi in hexane (1.65 M; 2.28 ml, 3.77 mmol) was addeddropwise at −78° C. over one hour, and was stirred at the sametemperature for additional one hour. To the reaction mixture formed,4-(4-propylcyclohexyl)cyclohexanone (756 mg, 3.40 mmol) in dry THF (5ml) was added dropwise over one hour. The reaction mixture was returnedto room temperature and further stirred for 5 hours. The reactionmixture was cooled to 0° C., to which was added slowly 2M-hydrochloricacid (2 ml). Toluene (30 ml) was added to the reaction mixture and wasstirred sufficiently. The separated organic layer was washed twice withsaturated brine (20 ml), and dried over anhydrous magnesium sulfate.Removal of the solvent under reduced pressure gave the title compound(1.53 g, 100%). This compound was used for the subsequent reactionwithout purification.

[0109] (3) Preparation of4-[4-(4-propylcyclohexyl)cyclohexe-1-yl]-2,3-bis(trifluoromethyl)-1-methoxybenzene

[0110] A mixture of4-[1-hydroxy-4-(4-propylcyclohexyl)cyclohexyl]-2,3-bis(trifluoromethyl)-1-methoxybenzene (1.5 g, 3.31 mmol), p-toluenesulfonicacid monohydrate (63 mg, 0.33 mmol) and toluene (15 ml) was placed in aJean-Stoke equipment and was heated under reflux for 3 hours whileremoving water produced. The reaction mixture obtained was returned toroom temperature, washed twice with water (15 ml) and dried overanhydrous magnesium sulfate. After the solid was removed by filtration,the solvent was removed under reduced pressure. The residue was purifiedby column chromatography (silica gel, an eluent is toluene) to give thetitle compound (1.22 g, 85%).

[0111] (4) Preparation of4-[4-(4-propylcyclohexyl)cyclohexyl]-2,3-bis(trifluoromethyl)-1-methoxybenzene

[0112] A mixture of4-[4-(4-propylcyclohexyl)cyclohexe-1-yl]-2,3-bis(trifluoromethyl)-1-methoxybenzene(1.2 g, 2.76 mmol), 5%-palladium carbon (120 mg) and ethanol (30 ml) wasstirred in an atmosphere of hydrogen for 12 hours. The catalyst wasremoved by filtration, and the filtrate was concentrated under reducedpressure. The residue was purified by column chromatography (silica gel,an eluent is toluene) and then recrystallized from ethanol five times togive the title compound (435 mg, 35%, colorless crystal).

Example 4

[0113]

[0114] (1) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenyl4-propylphenylthiocarboxylate

[0115] In an atmosphere of dry nitrogen, 4-propylbenzenedithiocarboxylic acid (1.7 g, 8.65 mmol) in dry THF (5 ml) was added toa suspension of 60%-sodium hydride (865 mg, 21.6 mmol) and dry THF (5ml) at 0° C. The reaction mixture was stirred for one hour at the sametemperature. 4-Methoxy-2,3-bis(trifluoromethyl)phenol (1.5 g, 5.77 mmol)in dry THF (5 ml) was added to the reaction mixture at 5° C. and wasstirred for additional one hour at the same temperature. After theaddition of iodine (6.0 g, 23.8 mmol) in dry THF (20 ml), the reactionmixture was stirred at room temperature for 24 hours. The reactionmixture was extracted with toluene (50 ml), the organic layer was washedwith 2M-hydrochloric acid (30 ml), saturated sodium thiosulfate (30 ml),and water (30 ml) successively, and dried over anhydrous magnesiumsulfate. After the solid was removed by filtration, the filtrate wasconcentrated under reduced pressure. The residue was purified by columnchromatography (silica gel, eluent is toluene/heptane=3/7) to give thetitle compound (640 mg, 26%, yellow crystals).

[0116] (2) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenylα,α-difluoro-4-propylbenzyl Ether

[0117] HF-pyridrine complex (900 mg) was added dropwise at −68° C. toNBS (420 mg, 2.36 mmol) in dry methylene chloride (5 ml). Then,4-methoxy-2,3-bis(trifluoromethyl)phenyl 4-propylphenyl thiocarboxylate(500 mg, 1.18 mmol) in dry methylene chloride (15 ml) was added at thesame temperature, and was stirred for one hour. The reaction mixtureobtained was poured into a saturated aqueous solution of sodium hydrogencarbonate (100 ml), the separated organic layer was washed with water(50 ml), and dried over anhydrous magnesium sulfate. After the solventwas removed under reduced pressure, the residue was purified by columnchromatography (silica gel; an eluent is toluene/heptane=3/7) to givethe title compound (221 mg, 44%, colorless oil). The R_(f) value of thiscompound was 0.46 (toluene) and dielectric anisotropy was −6.8(extrapolated).

[0118] Mp: 28. 2° C.

[0119]¹H-NMR (500 MHz, CDCl₃): δ 0.98 (t, ³J=7.3 Hz, 3H), 1.65-1.73 (m,2H), 2.67 (t, ³J=7.5Hz, 2H), 4.00 (s, 3H), 7.19-7.32 (m, 4H), 7.66-7.71(m, 2H).

[0120]¹⁹F-NMR (470 MHz, CDCl₃): δ −64.5 (d, ⁶J_(FF)=4.4 Hz, 2F), −56.1(q, ⁵J_(FF)=16.7 Hz, 3F), −54.1(q of t, ⁵J_(FF)=16.7 Hz, ⁶J_(FF)=4.4 Hz,3F).

[0121] MS(70 eV, EI), m/z(%):428(7, M⁺), 409(7, M⁺-F), 169 (100).

Example 5

[0122]

[0123] (1) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenylTrans-4-(trans-4-propylcyclohexyl)cyclohexylthiocarboxylate

[0124] In an atmosphere of dry nitrogen,4-methoxy-2,3-bis(trifluoromethyl)phenyl4-(4-propylcyclohexyl)cyclohexanecarboxylate (7.0 g, 14.2 mmol) preparedin Example 1, and2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetan-2,4-disulfide(Lawesson's reagent, 8.6 g, 21.3 mmol) were added to mesitylene (50 ml),and was stirred at 160° C. for 7 hours. After cooling gradually to roomtemperature and adding water (100 ml), the mixture was extracted withtoluene (200 ml). The extract was washed successively with a saturatedaqueous solution of sodium carbonate (50 ml) and then water (50 ml), anddried over anhydrous magnesium sulfate. After the solvent was removedunder reduced pressure, the residue was purified by columnchromatography (silica gel, an eluent is toluene/heptane=3/7) to givethe title compound (2.1 g, 29%, yellow crystals).

[0125] (2) Preparation of 4-methoxy-2,3-bis(trifluoromethyl)phenylα,α-difluoro-α-(trans-4-(trans-4-propylcyclohexyl)cyclohexyl)methylEther

[0126] HF-pyridine complex (3.0 g) was added dropwise at −68° C. to NBS(1.4 mg, 7.9 mmol) in dry methylene chloride (15 ml). Then,4-methoxy-2,3-bis(trifluoromethyl)phenyltrans-4-(trans-4-propylcyclohexyl)cyclohexylthiocarboxylate (2.0 g, 3.9mmol) in dry methylene chloride (30 ml) was added at the sametemperature and the mixture was stirred for additional one hour. Thereaction mixture obtained was poured into a saturated aqueous solutionof sodium hydrogencarbonate (300 ml), the separated organic layer waswashed with water (150 ml), and dried over anhydrous magnesium sulfate.After the solvent was removed under reduced pressure, the residue waspurified by column chromatography (silica gel, an eluent istioluene/heptane=3/7) to give the title compound (830 mg, 41%, colorlesscrystals). The R_(f) value of this compound was 0.56(toluene/heptane=3/7) and dielectric anisotropy was −7.2 (extrapolated).

[0127] Cr 99.3 N 118.5 I.

[0128]¹H-NMR (500 MHz, CDCl₃): δ 0.87 (t, ³J=7.4 Hz, 3H), 0.96-1.16 (m,11H), 1.25-1.40 (m, 4H), 1.68-1.78 (m, 4H), 1.81-1.87 (m, 2H), 1.99-2.06(m, 3H), 3.93 (s, 3H), 7.20 (d, ³J=9.4 Hz, 1H), 7.53 (d, ³J=9.4 Hz, 1H).

[0129]¹⁹F-NMR (470 MHz, CDCl₃):δ −77.92˜−77.85 (m, 2F), −56.1 (q,⁵J_(FF)=16.5 Hz, 3F), −54.3(qof t, ⁵J_(FF)=16.5 Hz, ⁶J_(FF)=3.8 Hz, 3F).

[0130] MS(70 eV, EI), m/z(%): 516(9, M⁺), 260 (100).

Example 6

[0131] The following compounds are prepared in a manner similar to thosedescribed in Examples 1 to 5. The compounds prepared in Examples 1 to 5are also exemplified. Among these compounds, there are compounds having—(CH₂)₂— as a bonding group. It is possible to prepare the correspondingcompounds having —C≡C—, —(CH₂)₃—O— or —O—(CH₂)₃— instead of thecompounds having —(CH₂)₂—In these compounds, a black dot shows that theconfiguration is trans. A value of dielectric anisotropy is obtained byextrapolating a measured value.

TABLE 1 Method for Description of Compounds Using Symbols

1) Left Terminal Group R- Symbol 3) Bonding Group —Zn— SymbolC_(n)H_(2n+1)— n- —C2H4— 2 C_(n)H_(2n+1)O— nO— —C4H8— 4C_(n)H_(2n+1)OC_(m)H_(2m+1)— nOm- —COO— E CH₂═CH— V— —C≡C— TCH₂═CHC_(n)H_(2n)— Vn- —CH═CH— V C_(n)H_(2n+1)CH═CHC_(m)H_(2m)— nVm-—CF₂O— CF2O C_(n)H_(2n+1)CH═CHC_(m)H_(2m)CH═CHC_(k)H_(2k)— nVmVk- —OCF₂—OCF2 CF₂═CH— VFF— CF₂═CHC_(n)H_(2n)— VFFn- 2) Ring Structure -An- Symbol4) Right Terminal Group -X Symbol

B —F —F

B(F) —Cl —CL

B(F, F) —CN —C

H —CF₃ —CF3

Ch —OCF₃ —OCF3

G —OCF₂H —OCF2H

Py —C_(n)H_(2n+1) -n

B(2F, 3F) —OC_(n)H_(2n+1) —On

B(2CN, 3CN) —COOCH₃ -EMe

B(2CF3, 3CF3) —C_(n)H_(2n)CH═CH₂ -nV —C_(m)H_(2m)CH═CHC_(n)H_(2n+1) -mVn—CH═CF₂ -VFF C_(n)H_(2n)CH═CF₂ -nVFF 5) Examples of Description Example1 3-H2B(F, F)B(F)-F

Example 2 2CF2O-B(F)BB-Cl

Example 3 3-GHEB(F, F)-F

[0132] Representative compositions of this invention are summarized inComposition Examples 1 to 21. The compounds which are components of acomposition are first shown with their respective amounts (weightpercent). For example, “4.0% ” in Composition Example 1 stands for 4.0weight percent. A symbol of “.” in 4.0% is a decimal point. Thecompounds are presented by the symbols of a left terminal group, abonding group, a ring structure, and a right terminal group, accordingto the rules in Table 1 described above. Configuration of1,4-cyclohexylene and 1,3-dioxane-2,5-diyl is trans. No symbol of aterminal group means that the terminal group is hydrogen. Next, physicalproperties of the composition are shown. The physical properties weremeasured based on the method described in the Standard of ElectricIndustries Association of Japan, EIAJ ED-2521A.

[0133] Phase transition temperature of nematic-isotropic liquid (NI; °C.): A sample was placed on a hot plate of a melting point apparatusequipped with a polarization microscope and was heated at the rate of 1°C. per minute. The temperature was measured when a part of the samplebegan to change from a nematic phase to isotropic liquid.

[0134] Viscosity (η; Measured at 20° C.; mPa·s):

[0135] E-type rotary viscometer was used for the measurement ofviscosity.

[0136] Optical Anisotropy (Refractive Index Anisotropy; Δn; Measured at25° C.):

[0137] Optical anisotropy was measured using Abbe refractometer by theaid of light having wavelength of 589 nanometers.

[0138] Dielectric Anisotropy (Δε; Measured at 25° C.)

[0139] 1) Composition Having a Value of Positive Δε: A sample was pouredinto a liquid crystal cell in which the gap between two glass plates is9 micrometers and a twist angle is 80 degrees. A dielectric constant(ε∥) that is parallel to a liquid crystal molecule was measured byapplying 20 volt to the cell. A dielectric constant (ε⊥) that isperpendicular to a liquid crystal molecule was measured by applying 0.5volt. A value of dielectric anisotropy was calculated from the formula:Δε=ε∥−ε⊥.

[0140] 2) Composition Having a Value of Negative Δε:

[0141] A sample was poured into a liquid crystal cell having homeotropicalignment and a dielectric constant (ε∥) was measured by applying 0.5volt. A sample was poured into a liquid crystal cell having homogeneousalignment and a dielectric constant (ε⊥) was measured by applying 0.5volt. A value of dielectric anisotropy was calculated from the formula:Δε=ε∥−ε⊥.

[0142] Threshold Voltage (Vth; Measured at 25° C; volt):

[0143] A sample was poured into a liquid crystal display element with anormally white mode, in which the gap between two glass plates was(0.5/Δn) micrometer and a twist angle was 80 degree. Δn is a value ofoptical anisotropy measured by the method described above. Rectanglewaves with a frequency of 32 Hz were applied to the element. Voltage ofthe rectangle waves was increased and a value of the voltage wasmeasured when the transmission of light passing through the elementbecame 90%. Composition Example 1 3-HHCF2OB(2CF3, 3CF3)-O1 4.0% 3-HEB-O428.0% 4-HEB-O2 20.0% 5-HEB-O1 20.0% 3-HEB-O2 18.0% 5-HEB-O2 10.0% NI =75.3 (° C.); η = 21.1 (mPa . s); Δn = 0.088. Composition Example 23-HB(2CF3, 3CF3)-O2 12.0% 5-HB(2CF3, 3CF3)-O2 11.0% 3-HH-2 5.0% 3-HH-46.0% 3-HH-O1 4.0% 3-HH-O3 5.0% 5-HH-O1 4.0% 3-HHB(2F, 3F)-O2 14.0%5-HHB(2F, 3F)-O2 15.0% 3-HHB(2F, 3F)-2 24.0% NI = 93.0 (° C.); Δn =0.074; Δε = −4.5. Composition Example 3 3-HHB(2CF3, 3CF3)-O2 12.0%5-HHB(2CF3, 3CF3)-O2 13.0% 3-HH-5 5.0% 3-HH-4 5.0% 3-HH-O1 6.0% 3-HH-O36.0% 3-HB-O1 5.0% 3-HB-O2 5.0% 3-HB(2F, 3F)-O2 10.0% 5-HB(2F, 3F)-O210.0% 3-HHB(2F, 3F)-2 4.0% 2-HHB(2F, 3F)-1 4.0% 3-HHEH-3 5.0% 3-HHEH-55.0% 4-HHEH-3 5.0% Composition Example 4 3-BCF2OB(2CF3, 3CF3)-O1 12.0%3-BB(2F, 3F)-O4 10.0% 5-BB(2F, 3F)-O4 10.0% 2-BB(2F, 3F)B-3 25.0%3-BB(2F, 3F)B-5 13.0% 5-BB(2F, 3F)B-5 14.0% 5-BB(2F, 3F)B-7 16.0% NI =70.5 (° C.); Δn = 0.198; Δε = −3.5. Composition Example 5 3-HHEB(2CF3,3CF3)-O1 9.0% 3-HHBB(2CF3, 3CF3)-O1 7.0% 3-HB-O1 15.0% 3-HB-O2 6.0%3-HEB(2F, 3F)-O2 9.0% 4-HEB(2F, 3F)-O2 9.0% 2-BB2B-O2 6.0% 3-BB2B-O26.0% 5-BB2B-O1 6.0% 5-BB2B-O2 6.0% 1-B2BB(2F)-5 7.0% 3-B2BB(2F)-5 7.0%5-B(F)BB-O2 7.0% NI = 91.3 (° C.); η = 35.1 (mPa . s); Δn = 0.151.Composition Example 6 3-HB(2CF3, 3CF3)-O2 16.0% 5-HB(2CF3, 3CF3)-O221.0% 3-HHB(2CF3, 3CF3)-O2 14.0% 5-HHB(2CF3, 3CF3)-O2 20.0% 3-HH-O1 8.0%5-HH-O1 4.0% 3-HH-4 5.0% 2-HHB(2F, 3F)-1 5.0% 3-HHB(2F, 3F)-1 7.0% NI =39.6 (° C.); Δn = 0.056; Δε = −5.8. Composition Example 7 3-HCF2OB(2CF3,3CF3)-O2 12.0% 3-HHCF2OB(2CF3, 3CF3)-O2 13.0% 3-HB-Cl 15.0% 3-HH-4 5.0%5-HB(2F, 3F)-O2 12.0% 2-HHB(2F, 3F)-1 12.0% 3-HHB(2F, 3F)-1 12.0%5-HHB(2F, 3F)-O2 13.0% 3-HHB-1 6.0% NI = 74.1 (° C.); η = 51.4 (mPa .s); Δn = 0.084; Δε = −3.6. Composition Example 8 3-HHB(2CF3, 3CF3)-O13.0% 5-HHB(2CF3, 3CF3)-O1 3.0% 3-HH1OB(2CF3, 3CF3)-O1 3.0% 5-HH1OB(2CF3,3CF3)-O2 3.0% 3-HB-O1 15.0% 3-HH-4 5.0% 3-HB(2F, 3F)-O2 12.0% 5-HB(2F,3F)-O2 12.0% 2-HHB(2F, 3F)-1 12.0% 3-HHB(2F, 3F)-O2 13.0% 5-HHB(2F,3F)-O2 13.0% 6-HEB(2F, 3F)-O2 6.0% Composition Example 9 3-HBB(2CF3,3CF3)-O1 3.0% 3-HB-O2 20.0% 1O1-HH-3 6.0% 1O1-HH-5 5.0% 3-HH-EMe 12.0%4-HEB-O1 9.0% 4-HEB-O2 7.0% 5-HEB-O1 8.0% 3-HHB-1 6.0% 3-HHB-3 6.0%6-HEN-O4 3.0% 3-HEN-O5 4.0% 4-HEN-O5 3.0% 5-HEN-O5 2.0% 2-HBEN-O2 2.0%4-HBEN-O4 4.0% Composition Example 10 3-HCF2OB(2CF3, 3CF3)-O2 3.0%3-HHCF2OB(2CF3, 3CF3)-O1 3.0% 1V2-BEB(F, F)-C 5.0% 3-HB-C 20.0% V2-HB-C6.0% 1-BTB-3 5.0% 2-BTB-1 10.0% 3-HH-4 11.0% 3-HHB-1 11.0% 3-H2BTB-24.0% 3-H2BTB-3 4.0% 3-H2BTB-4 4.0% 3-HB(F)TB-2 6.0% 3-HB(F)TB-3 5.0%3-HHB-C 3.0% NI = 88.4 (° C.); η = 19.9 (mPa . S); Δn = 0.161; Δε = 6.7;Vth = 2.14 (V). Composition Example 11 3-BCF2OB(2CF3, 3CF3)-O1 4.0%3-HBCF2OB(2CF3, 3CF3)-O1 4.0% 2-BEB(F)-C 5.0% 3-BEB(F)-C 4.0% 4-BEB(F)-C12.0% 1V2-BEB(F, F)-C 16.0% 3-HB-O2 6.0% 3-HH-4 3.0% 3-HHB-F 3.0%3-HHB-1 4.0% 3-HHB-O1 4.0% 3-HBEB-F 4.0% 3-HHEB-F 7.0% 5-HHEB-F 7.0%3-H2BTB-2 4.0% 3-H2BTB-3 4.0% 3-H2BTB-4 4.0% 3-HB(F)TB-2 5.0% NI = 81.3(° C.); η = 46.8 (mPa . S); Δn = 0.141; Δε = 27.5; Vth = 1.06 (V).Composition Example 12 5-HB(2CF3, 3CF3)-O2 10.0% 3-HHB(2CF3, 3CF3)-O210.0% 2-HB-C 5.0% 3-HB-C 12.0% 3-HB-O2 5.0% 2-BTB-1 3.0% 3-HHB-1 8.0%3-HHB-F 4.0% 3-HHB-Cl 5.0% 3-HHB-3 4.0% 3-HHEB-F 4.0% 5-HHEB-F 4.0%2-HHB(F)-F 7.0% 3-HHB(F)-F 7.0% 5-HHB(F)-F 7.0% 3-HHB(F, F)-F 5.0%Composition Example 13 3-HB(2CF3, 3CF3)-O2 3.0% V2-HB-C 12.0% 1V2-HB-C12.0% 3-HB-C 24.0% 3-HB(F)-C 5.0% 2-BTB-1 2.0% 3-HH-4 5.0% 3-HH-VFF 6.0%2-HHB-C 3.0% 3-HHB-C 6.0% 3-HB(F)TB-2 8.0% 3-H2BTB-2 5.0% 3-H2BTB-3 5.0%3-H2BTB-4 4.0% NI = 86.7 (° C.); η = 20.6 (mPa . s); Δn = 0.155; Δε =8.6; Vth = 2.00 (V). Composition Example 14 3-HHB(2CF3, 3CF3)-O2 3.0%5-HHB(2CF3, 3CF3)-O2 3.0% 3-HBB(2CF3, 3CF3)-O1 3.0% 1V2-BEB(F, F)-C 6.0%3-HB-C 18.0% 2-BTB-1 10.0% 5-HH-VFF 30.0% 1-BHH-VFF 8.0% 1-BHH-2VFF 2.0%3-H2BTB-2 5.0% 3-H2BTB-3 4.0% 3-H2BTB-4 4.0% 3-HHB-1 4.0% CompositionExample 15 3-HHEB(2CF3, 3CF3)-O1 3.0% 3-HH1OB(2CF3, 3CF3)-O1 3.0%5-HH1OB(2CF3, 3CF3)-O2 3.0% 5-HBCF2OB(F, F)-C 3.0% 5-HB(F, F)CF2OB(F,F)-C 3.0% 3-HB-C 18.0% 2-BTB-1 10.0% 5-HH-VFF 30.0% 1-BHH-VFF 8.0%1-BHH-2VFF 2.0% 3-H2BTB-2 5.0% 3-H2BTB-3 4.0% 3-H2BTB-4 4.0% 3-HHB-14.0% Composition Example 16 3-HCF2OB(2CF3, 3CF3)-O1 4.0% 3-HHCF2OB(2CF3,3CF3)-O1 4.0% 3-HB-CL 16.0% 3-HH-4 12.0% 3-HH-5 4.0% 3-HHB-F 4.0%3-HHB-CL 3.0% 4-HHB-CL 4.0% 3-HHB(F)-F 10.0% 4-HHB(F)-F 9.0% 5-HHB(F)-F9.0% 5-HBB(F)-F 4.0% 5-HBBH-1O1 3.0% 3-HHB(F, F)-F 2.0% 4-HHB(F, F)-F3.0% 5-HHB(F, F)-F 3.0% 3-HH2BB(F, F)-F 3.0% 4-HH2BB(F, F)-F 3.0% NI =111.0 (° C.); η =23.9 (mPa . s); Δn = 0.090; Δε = 2.8; Vth = 3.06 (V).Composition Example 17 3-HB(2CF3, 3CF3)-O2 5.0% 5-HHB(2CF3, 3CF3)-O25.0% 5-HB-F 12.0% 6-HB-F 9.0% 7-HB-F 7.0% 2-HHB-OCF3 7.0% 3-HHB-OCF37.0% 4-HHB-OCF3 7.0% 5-HHB-OCF3 5.0% 3-HH2B-OCF3 4.0% 5-HH2B-OCF3 4.0%3-HHB(F, F)-OCF3 5.0% 3-HBB(F)-F 10.0% 3-HH2B(F)-F 3.0% 3-HB(F)BH-3 3.0%5-HBBH-3 3.0% 3-HHB(F, F)-OCF2H 4.0% Composition Example 18 3-HH2B(2CF3,3CF3)-O1 2.0% 5-HH2B(2CF3, 3CF3)-O2 2.0% 3-HH1OB(2CF3, 3CF3)-O1 2.0%5-HH1OB(2CF3, 3CF3)-O2 2.0% 7-HB(F)-F 5.0% 5-H2B(F)-F 5.0% 3-HB-O2 10.0%3-HH-4 5.0% 2-HHB(F)-F 10.0% 3-HHB(F)-F 10.0% 5-HHB(F)-F 10.0%3-H2HB(F)-F 5.0% 2-HBB(F)-F 3.0% 3-HBB(F)-F 3.0% 5-HBB(F)-F 6.0%2-H2BB(F)-F 5.0% 3-H2BB(F)-F 6.0% 3-HHB-O1 5.0% 3-HHB-3 4.0% CompositionExample 19 3-BCF2OB(2CF3, 3CF3)-O1 5.0% 7-HB(F, F)-F 5.0% 3-H2HB(F, F)-F12.0% 4-H2HB(F, F)-F 6.0% 3-HHB(F, F)-F 10.0% 3-HBB(F, F)-F 10.0%3-HHEB(F, F)-F 10.0% 4-HHEB(F, F)-F 3.0% 5-HHEB(F, F)-F 3.0% 2-HBEB(F,F)-F 3.0% 3-HBEB(F, F)-F 5.0% 5-HBEB(F, F)-F 3.0% 3-HGB(F, F)-F 15.0%3-HBCF2OB-OCF3 4.0% 3-HHBB(F, F)-F 6.0% NI = 69.7 (° C.); η = 36.3 (mPa. s); Δn = 0.084; Δε = 12.3; Vth = 1.45 (V). Composition Example 203-HHEB(2CF3, 3CF3)-O1 4.0% 3-HHBB(2CF3, 3CF3)-O1 4.0% 7-HB(F)-F 7.0%5-HB-CL 3.0% 3-HH-4 9.0% 3-HH-EMe 23.0% 3-HHEB(F, F)-F 10.0% 4-HHEB(F,F)-F 5.0% 3-HHEB-F 8.0% 4-HGB(F, F)-F 5.0% 5-HGB(F, F)-F 6.0% 2-H2GB(F,F)-F 4.0% 3-H2GB(F, F)-F 5.0% 5-GHB(F, F)-F 7.0% NI = 78.6 (° C.); η =27.3 (mPa . S); Δn = 0.064; Δε = 4.6; Vth = 2.03 (V). CompositionExample 21 5-HB(2CF3, 3CF3)-O2 5.0% 3-HHB(2CF3, 3CF3)-O2 8.0%5-HHB(2CF3, 3CF3)-O2 11.0% 3-HB(F, F)CF2OB(F, F)-F 15.0% 3-BB(F,F)CF2OB(F, F)-F 15.0% 3-HBB(F, F)-F 15.0% 5-HBB(F, F)-F 12.0% 3-HHB(F,F)-F 8.0% 2-HHBB(F, F)-F 3.0% 3-HHBB(F, F)-F 5.0% 5-HHBB(F, F)-F 3.0%

[0144] In Composition Example 10 described above, when the opticallyactive compound (Op-4) of 0.8 wt % based on the composition was added tothe composition, the value of the pitch was 11.3 micrometers. InComposition Example 19 described above, when the optically activecompound (Op-5) of 0.25 wt % based on the composition was added to thecomposition, the value of the pitch was 62.3 micrometers.

EFFECT OF THE INVENTION

[0145] The liquid crystal compound of this invention is stablechemically and has excellent miscibility with other liquid crystalcompounds, large and negative dielectric anisotropy, and proper opticalanisotropy. The composition comprising the compound has large specificresistance and a large voltage holding ratio, and the composition isuseful for a liquid crystal display element.

What is claimed is:
 1. A liquid crystal compound represented by formula(1): RaA₁—Z₁_(m)A₂—Z₂_(n)—A₃—Z₃—A₄—Rb  (1) wherein Ra and Rbindependently are alkyl having 1 to 20 carbons, any —CH₂— in the alkylmay be replaced by —O—, —S—, —CH═CH—, or —C≡C—, and any hydrogen may bereplaced by halogen; A₁, A₂, A₃, and A₄ independently are1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl,1,4-phenylene, pyridine-2,5-idiyl, pyrimidine-2,5-diyl,pyridazine-3,6-diyl, or 2,3-bis(trifluoromethyl)-1,4-phenylene, anyhydrogen in these rings may be replaced by halogen, and at least one ofA₁, A₂, A₃, and A₄ is 2,3-bis(trifluoromethyl)-1,4-phenylene; Z₁, Z₂ andZ₃ independently are a single bond, —(CH₂)₂—, —(CF₂)₂—, —COO—, —OCO—,—CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CH═CH—, —CF═CF—, —C≡C—, —(CH₂)₄—,—(CH₂)₃O—, or —O(CH₂)₃—; m and n independently are 0 or
 1. 2. Thecompound according to claim 1 wherein m and n are 0 in formula (1)described in claim
 1. 3. The compound according to claim 1 wherein m is0 and n is 1 in formula (1) described in claim
 1. 4. The compoundaccording to claim 1 wherein m is 1 and n is 1 in formula (1) describedin claim
 1. 5. The compound according to any one of claims 1 to 4wherein Ra and Rb independently are alkyl having 1 to 20 carbons, alkoxyhaving 1 to 19 carbons or alkenyl having 2 to 21 carbons.
 6. Thecompound according to any one of claims 2 to 4 wherein Ra and Rbindependently are alkyl having 1 to 20 carbons, alkoxy having 1 to 19carbons or alkenyl having 2 to 21 carbons; and Z₁, Z₂ and Z₃independently are a single bond, —(CH₂)₂—, —(CH₂)₄—, —CF₂O—, or —OCF₂—.7. The compound according to claim 6 wherein at least one of Z₁, Z₂ andZ₃ is —CF₂O—.
 8. A compound represented by formulas (a) to (m):

wherein Ra and Rb independently are alkyl having 1 to 20 carbons, any—CH₂— in the alkyl may be replaced by —O— or —CH═CH—, and any hydrogenmay be replaced by halogen; A₁, A₂, A₃, and A₄ independently are1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl,1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene,2,5-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene,2,3,5-trifluoro-1,4-phenylene, 2,3,5,6-tetrafluoro-1,4-phenylene,pyridine-2,5-diyl, 3-fluoropyridine-2,5-diyl, pyrimidine-2,5-diyl,pyridazine-3,6-diyl, or 2,3-bis(trifluoromethyl)-1,4-phenylene, and atleast one of A₁, A₂, A₃, and A₄ is2,3-bis(trifluoromethyl)-1,4-phenylene; Z₁, Z₂ and Z₃ independently area single bond, —(CH₂)₂—, —(CF₂)₂—, —COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—,—OCF₂—, —CH═CH—, —CF═CF—, —C≡C—, —(CH₂)₄—, —(CH₂)₃O—, or —O(CH₂)₃—; andm and n independently are 0 or
 1. 9. A liquid crystal compositioncomprising at least one compound described in claim
 1. 10. Thecomposition according to claim 9, further comprising at least onecompound selected from the group consisting of the compounds representedby formulas (2), (3) and (4):

wherein R¹ is alkyl having 1-10 carbons, any —CH₂— in the alkyl may bereplaced by —O— or —CH═CH—, and any hydrogen may be replaced byfluorine; X¹ is fluorine, chlorine, —OCF₃, —OCHF₂, —CF₃, —CHF₂, —CH₂F,—OCF₂CHF₂, or —OCF₂CHFCF₃; rings B and D independently are1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or 1,4-phenylene in which anyhydrogen may be replaced by fluorine; ring E is 1,4-cyclohexylene or1,4-phenylene in which any hydrogen may be replaced by fluorine; and Z⁴and Z⁵ independently are —(CH₂)₂—, —(CH₂)₄—, —COO—, —CF₂O—, —OCF₂—,—CH═CH—, or a single bond; and L¹ and L² independently are hydrogen orfluorine.
 11. The composition according to claim 9, further comprisingat least one compound selected from the group consisting of thecompounds represented by formulas (5) and (6):

wherein R² and R³ independently are alkyl having 1 to 10 carbons, any—CH₂— in the alkyl may be replaced by —O— or —CH═CH— and any hydrogenmay be replaced by fluorine; X² is —CN or —C≡C—CN; ring G is1,4-cyclohexylene, 1,4-phenylene, 1,3-dioxane-2,5-diyl, orpyrimidine-2,5-diyl; ring J is 1,4-cyclohexylene, pyrimidine-2,5-diyl or1,4-phenylene in which any hydrogen may be replaced by fluorine; ring Kis 1,4-cyclohexylene or 1,4-phenylene; Z⁶ is —(CH₂)₂—, —COO—, —CF₂O—,—OCF₂—, or a single bond; L³, L⁴ and L⁵ independently are hydrogen orfluorine; and b, c and d independently are 0 or
 1. 12. The compositionaccording to claim 9, further comprising at least one compound selectedfrom the group consisting of the compounds represented by formulas (7),(8) and (9):

wherein R⁴ and R⁵ independently are alkyl having 1 to 10 carbons, any—CH₂— in the alkyl may be replaced by —O— or —CH═CH—,and any hydrogenmay be replaced by fluorine; rings M and P independently are1,4-cyclohexylene or 1,4-phenylene; Z⁷ and Z⁸ independently are—(CH₂)₂—, —COO— or a single bond; L⁶ and L⁷ independently are hydrogenor fluorine, and at least one of L⁶ and L⁷ is fluorine.
 13. Thecomposition according to claim 10, further comprising at least onecompound selected from the group consisting of the compounds representedby formulas (10), (11) and (12):

wherein R⁶ and R⁷ independently are alkyl having 1 to 10 carbons, any—CH₂— in the alkyl may be replaced by —O— or —CH═CH—, and any hydrogenmay be replaced by fluorine; rings Q, T and U independently are1,4-cyclohexylene, pyrimidine-2,5-diyl or 1,4-phenylene in which anyhydrogen may be replaced by fluorine; Z⁹ and Z¹⁰ independently are—C≡C—, —COO—, —(CH₂)₂—, —CH═CH—, or a single bond.
 14. The compositionaccording to claim 11, further comprising at least one compound selectedfrom the group consisting of the compounds represented by formulas (10),(11) and (12) described in claim
 13. 15. The composition according toclaim 12, further comprising at least one compound selected from thegroup consisting of the compounds represented by formulas (10), (11) and(12) described in claim
 13. 16. The composition according to claim 13,further comprising at least one compound selected from the groupconsisting of the compounds represented by formulas (5) and (6)described in claim
 11. 17. The composition according to claim 9, furthercomprising at least one optically active compound.
 18. A liquid crystaldisplay element comprising the composition described in any one ofclaims 9 to 16.